A melt-surface initial position adjusting apparatus which is suitable for use in a monocrystal growing system employing the Czochralski method to adjust the vertical position of the melt surface before the growing of a monocrystal. The apparatus can ensure a highly precise measurement of a crystal-diameter measuring device, thereby enabling a reduction in the costs of producing a monocrystal bar. Before the growing of a crystal, the vertical position (H) of the surface (16A) of a melt within a crucible is measured. The crucible is moved vertically on the basis of the measured value in such a manner as to maintain the distance (L) between the melt surface (16A) and an image sensor (28) for measuring the crystal diameter at a predetermined value.